1. Technical Field
The invention relates to a process for desulfurizing a sour hydrocarbon feedstock with hydrogen to produce a low sulfur hydrocarbon product, sulfur and by-products, from which hydrogen is regenerated for the desulfurization step.
2. Background Art
Many hydrocarbon feedstocks contain relatively high concentrations of sulfur, which limit the utility of the feedstock. In order to enhance the utility of the feedstock it is necessary to remove the sulfur contained therein.
A conventional process for the desulfurization of a sour feedstock includes contacting the feedstock with hydrogen gas in the presence of a catalyst to generate a hydrocarbon product having a relatively low sulfur concentration and a gaseous by-product consisting primarily of hydrogen sulfide. Conventional desulfurization of the sour feedstock has several inherent shortcomings. First of all, conventional desulfurization requires hydrogen gas which is usually obtained from the partial oxidization of a hydrocarbon fuel. This requires an oxygen feed in addition to the hydrocarbon fuel which is cryogenically extracted from air in a very expensive process. Handling of the hydrodesulfurization by-product, which is a gas consisting primarily of hydrogen sulfide, is also a significant problem.
The by-product gas is generally oxidized directly with air via the Claus process to produce sulfur and water. However, the Claus process has a number of inherent disadvantages. For example, it operates at high temperatures, it requires exacting process control over the ratio of oxygen to hydrogen sulfide in the feed, and the annual maintainence costs for the Claus Process are typically 20% of the initial capital investment. Finally the sulfur content of Claus process tail gas released to the atmosphere is generally too high to meet stringent environmental regulations. To comply with these regulations, it is necessary to have several Claus stages and to employ separate tail gas clean-up processes at great expense.
The art is rife with modified Claus processes and other hydrogen sulfide oxidization processes which attempt to overcome the deficiences of the basic Claus process. Hydrogen sulfide oxidization processes, which include U.S. Pat. No. 2,819,950 to Patton, U.S. Pat. No. 3,311,453 to Lusby and U.S. Pat. No. 3,923,966 to Vaughan, have not substantially overcome the deficiencies of the basic Claus process.
A process is needed for desulfurizing a sour hydrocarbon feedstock with hydrogen gas, which can provide an economic source of hydrogen gas and which also converts the by-product gases to useful, environmentally-acceptable products.